How to Manage a Quarter Crack in Equine Hooves

Lameness caused by quarter cracks is a nemesis of horses and owners, and treatment is often a complex and time-consuming process. At the 2010 American Association of Equine Practitioners Convention, held Dec. 4-8 in Baltimore, Md., Steve O'Grady, BVSc, MRCVS, of Northern Virginia Equine, in Marshall, discussed the importance of these injuries and how, with exception of traumatic injury cases, it's rare to see a quarter crack without a concurrent sheared heel.

O'Grady described sheared heels as a common hoof capsule deformation caused by disproportionate loading on one side of the foot. This results in one heel bulb displacing upward relative to the adjacent heel bulb. Tissue on the displaced side between the hoof wall and surface of the short pastern bone changes shape, resulting in constant foot pain in the back of the hoof. Over time, uneven loading leads to hoof capsule distortion, subsolar bruising, corns, hoof wall separation, and quarter cracks.

According to O'Grady, veterinarians and farriers should target and correct sheared heel conformation by stabilizing the heels and repairing the crack. He explained that the hoof capsule's viscoelastic nature normally allows it to deform when stress is applied; yet, hoof capsule distortion occurs when compressive and shear forces exceed its capacity to deform.

This overload of the heel creates structural changes that make the hoof more upright, he explained. This decreases the foot's ground surface contact, the hoof wall straightens, heels contract, and the foot narrows. The overloaded heel rolls under with a hoof wall flare developing on the opposite side of the foot. The ungual (collateral) cartilage (on either side of the coffin bone, thought to function in hoof expansion/shock absorption) becomes trapped on the displaced side, restricting hoof expansion.

Radiographs of affected feet show the solar surface of the coffin bone positioned in an appropriate horizontal relationship with the ground, indicating that the heel disparity originates behind the body of the coffin bone. Trimming heels unevenly has been blamed as a cause of sheared heels, however O'Grady emphasized that the viscoelastic nature of the hoof capsule negates this effect--normally, the hoof accommodates trimming imbalances. Instead, limb conformation seems to be a key cause, especially if there is rotational limb deformity of the forelimbs, in particular toed-out conformation due to carpus valgus (outward rotation of the cannon bone at the knees). Limb conformation dictates hoof flight path and landing; hoof capsule deformation thus is an adaption to limb conformation--excess impact leads to disease.

O'Grady's objective is to trim and shoe the foot to improve hoof landing--to unload the displaced side of the foot, engage the frog, and lower the side of the displaced hoof capsule to increase ground surface contact. The trimmed foot should end up as wide as it is long. Then, additional horn is trimmed from the affected quarter back to the heel and a bar shoe applied. Impression material beneath a leather pad further improves frog loading, he noted. Within a month's time, improvement is usually measured as ¼ - ¾-inch growth at the coronary band that causes the heels to even out.

The displaced coronary band must be allowed to relax for 24 hours before repairing the crack with an implant. O'Grady suggests that veterinarians and farriers consider full thickness quarter cracks a type of fracture necessitating stabilization with implant wires and placement of a composite patch over the top of the wire repair.

O'Grady said he cannot overemphasize enough the importance of determining the underlying cause and implementing the appropriate farriery when managing a quarter crack. Veterinarians and farriers should assess limb conformation, improve foot conformation, and apply the appropriate shoe to repair the defect.

About the Author

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado,
and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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